CN106940431A - MR imaging apparatus, RF method for shimming and MR imaging method - Google Patents

MR imaging apparatus, RF method for shimming and MR imaging method Download PDF

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CN106940431A
CN106940431A CN201611106574.2A CN201611106574A CN106940431A CN 106940431 A CN106940431 A CN 106940431A CN 201611106574 A CN201611106574 A CN 201611106574A CN 106940431 A CN106940431 A CN 106940431A
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pulses
shimming
magnetic field
shimming parameter
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CN106940431B (en
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伊藤公辅
泷泽将宏
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Fujifilm Healthcare Corp
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Hitachi Ltd
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    • A61B5/0263—Measuring blood flow using NMR
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Abstract

For the image pickup part of MRI device NMR signal is collected using the high-frequency impulse including the excitation RF pulses for entering row energization comprising the preparation RF pulses for entering row energization to first area and pair second area different from above-mentioned first area, the shimming parameter calculating section for calculating the shimming parameter being adjusted to the irradiation Distribution of Magnetic Field that the high-frequency impulse by being irradiated from multiple passages is produced sets different shimming parameters respectively to preparation RF pulses and excitation RF pulses, and image pickup part is imaged using with the preparation RF pulses after different shimming parameter adjustments and excitation RF pulses.

Description

MR imaging apparatus, RF method for shimming and MR imaging method
Technical field
The present invention relates to MR imaging apparatus (hereinafter referred to as MRI device), more particularly to use to defined signal The camera technique of the suppressor pulse suppressed.
Background technology
MRI device is measured from the atomic nucleus being present in organism, the predominantly NMR signal from proton, to structure Atom cuclear density (proton density), the phase information of NMR signal into bio-tissue carry out the device of image conversion.In MRI dresses In putting, exploitation has the blood flow camera method of the difference of the behavior of the various protons that make use of blood flow proton and static tissue, and then The difference using blood flow direction is widely used for, the technology of desired blood flow is described with the brightness higher than other blood flows.Example Such as, have and the blood flow proton in upstream side or downstream carried out preparing excitation, suppress to enter the signal of the blood flow of camera watch region, So that technology that vein and artery are separated etc..
In this technology, in order to suppress the signal from unwanted blood flow, using making unwanted blood flow in advance The RF pulses that proton saturation carrys out attenuated signal (are referred to as presaturation pulse：presaturation pulse).In the method can Artery and vein are separated, but optionally can not only describe the desired part among multiple arteries or vein.On the other hand, It also developed and combine come the method for only entering row energization to desired position that (2D swashs by RF pulses and regional choice leaning magnetic field Encourage method).For example in patent document 1 propose following technology：When the travel condition of the blood vessel to incidence carries out image conversion, Using 2D advocate approach, suppress the signal of an arteria carotis among 2 arteria carotis, only describe another arteria carotis.
On the other hand, in current MRI device, shone using the multichannel transmit coil of multiple small coils is combined with Penetrate RF pulses.In this case, in excitation RF pulses, to the region of row energization to be entered, have and want to make illuminated magnetic field (shine Penetrate magnetic field) spatially consistent requirement.If this is because, there is distribution in excitation field, resulting from this and coming Produce uneven in the NMR signal of self-organizing, can not just obtain the distribution of correct proton, phase information.Therefore, existing In MRI device, the Distribution of Magnetic Field using the RF pulses generations irradiated from each passage is measured in advance, calculated for making magnetic field The correcting value of distribution uniformity, the correcting value (patent document 2) is superimposed to producing the driving voltage of RF coils of RF pulses.The school Positive quantity is referred to as RF shimmings parameter (hereinafter referred to as shimming parameter).
Prior art literature
Patent document
Patent document 1：International Publication 201I/037064
Patent document 2：TOHKEMY 2010-29640 publications
Invent problem to be solved
In the case of the desired artery among only describing the blood flow from multiple arteries, in above-mentioned 2D advocate approach In, by special shape (envelope：Envelope RF pulses and leaning magnetic field pulse combined) gets up to be applied, and only encourages quilt The region of restriction carries out presaturation, therefore RF shimmings can omit.But, due to passing through RF pulses and leaning magnetic field pulse Combine to enter row energization, therefore there is the problem of pulse application time length needed for presaturation is such.
The content of the invention
The present invention is in the shooting using preparation RF pulses and excitation RF pulses, by using to defined tissue or portion There are the different shimming parameters of different-effect to adjust these RF pulses for position, so as to will not cause prolonging for pulse application time It is long, another can be depicted with high brightness relative to one within two tissues or position.For example, for preparation RF arteries and veins Punching, in the region encouraged by it, is adjusted to shimming parameter, so as to it is compared in multiple positions a position The irradiation Distribution of Magnetic Field that his position irradiation magnetic field diminishes, for excitation RF pulses, adjusts shimming parameter to cause energized area Domain integrally turns into uniform irradiation Distribution of Magnetic Field.
Invention effect
Present invention is suitably applied to blood flow shooting.
Brief description of the drawings
Fig. 1 is figure of the expression using an embodiment of the MRI device of the present invention.
The figure of one embodiment of the transmit coil that Fig. 2 uses for expression in of the invention.
Fig. 3 is the functional block diagram of the operational part of the MRI device of first embodiment.
Fig. 4 is the figure of one of the pulse train used in the first embodiment.
The figure of the relation of first area and second area in image capture methods of the Fig. 5 to illustrate first embodiment.
Fig. 6 is the flow chart of the action for the operational part for representing first embodiment.
Fig. 7 is shown in neck layer image to represent the figure for the ROI input picture examples specified in first embodiment Upper specified two ROI situation.
Fig. 8 (a), (b) represent first embodiment in initial illumination Distribution of Magnetic Field and adjusted using shimming parameter Irradiation Distribution of Magnetic Field after whole.
The figure for the image example that Fig. 9 is imaged for expression by the MRI device of first embodiment, (a) is without progress presaturation In the case of head image, (b) is the head image that is suppressed to the signal from right carotid, (c) for from The head image that the signal of left neck artery is suppressed.
The figure of ROI settings in variations of the Figure 10 to illustrate first embodiment.
Figure 11 is the flow chart of the action for the operational part for representing second embodiment.
Between shooting that Figure 12 performs for the MRI device that represents by second embodiment and the image obtained by the shooting Relation figure.
The figure of the relation between first area and second area in image capture methods of the Figure 13 to illustrate the 3rd embodiment.
The figure of one of the pulse train that Figure 14 is used in the third embodiment for expression.
The explanation of symbol
1 detected body, 2 magnetostatic field generating units, 3 leaning magnetic field generating units (image pickup part), 4 sequencers (image pickup part), 5 Sending part (image pickup part), 57 transmit coils, 6 acceptance divisions (image pickup part), 7 signal processing parts, 73 display parts (display), 75 inputs Portion, 8 operational parts, 81 ROI configuration parts, 82 irradiation magnetic field calculating sections, 83 shimming parameter calculating sections, 84 imaging control parts, 85 images Reconstructing part, 87 display control units, 89 memories, 411 suppress RF pulses (preparation RF pulses), 421 excitation RF pulses, 400 TOF Pulse train, 510 first areas, 520 second areas, 800 ASL sequences, the RF pulses (preparation RF pulses) of 801 marks, 802 Encourage RF pulses
Embodiment
Illustrate the summary of embodiments of the present invention.
The MRI device of present embodiment possesses：With the multichannel that high-frequency impulse is irradiated from each passage of multiple passages Transmit coil, using the preparation RF pulses for entering row energization comprising the first area to detected body and pair with above-mentioned first area not With the second area high-frequency impulse that enters including the excitation RF pulses of row energization collect the image pickup part of NMR signal；And calculate The shimming for the shimming parameter being adjusted to the irradiation Distribution of Magnetic Field that the high-frequency impulse by being irradiated from above-mentioned multiple passages is produced Parameter calculating section.
Above-mentioned shimming parameter calculating section is calculated and as the second of the shimming parameter for being configured to above-mentioned excitation RF pulses The first different shimming parameter of shimming parameter, is used as the shimming parameter of above-mentioned prepared RF pulses, above-mentioned image pickup part use with Preparation RF pulses that above-mentioned first shimming parameter is adjusted and the excitation RF adjusted with above-mentioned second shimming parameter Pulse is imaged.
Shimming parameter calculating section calculates above-mentioned first shimming parameter, to cause for example by above-mentioned prepared RF pulses above-mentioned The irradiation Distribution of Magnetic Field produced in first area is smaller than the irradiation magnetic field of second position for the irradiation magnetic field of first position.In addition, So-called irradiation magnetic field (B1) be big/small to refer to that its intensity (| B1 |) is big/small.
Existing RF shimmings are to set shimming parameter to cause the irradiation Distribution of Magnetic Field in image pickup part position uniform, relative to existing The setting of some RF shimmings, the MRI device of present embodiment is made based on preparation by being set in desired position (first position) The shimming parameter that the irradiation Distribution of Magnetic Field of RF pulses diminishes, selection is carried out so as to excitation RF pulses after passage and is swashed In the shooting position encouraged, optionally describe the desired position.Or, driving pulse that can be after passage is selected In the shooting position for selecting excitation, optionally describe the position beyond the desired position.
Next, the overall structure of the MRI device to applying present embodiment is illustrated.Fig. 1 is this implementation of expression The integrally-built block diagram of the MRI device of mode.As shown in this figure, the MRI device 100 of present embodiment possesses：It is magnetostatic Generating unit 2, leaning magnetic field generating unit 3, sequencer 4, sending part 5, acceptance division 6, signal processing part 7, operational part 8 and Load the sleeping platform 9 of detected body 1.
Magnetostatic field generating unit 2 is that the space for being placed detected body 1 produces the device of uniform magnetostatic field, and it possesses forever Magnet mode, the magnetostatic field generation device for often leading mode or superconducting fashion.According to the difference in the direction of magnetostatic field, there is perpendicular magnetic Field type and horizontal magnetic field mode, according to the difference of its mode, the shape of the magnet included in magnetostatic field generation device, encirclement should The stand shape of magnet is different.In the present invention, the magnetostatic field generation device of which kind of mode is all not limited, and can be applied.
Leaning magnetic field generating unit 3 forms magnetic field gradient in the magnetostatic field space that magnetostatic field generating unit 2 is formed, and possesses 3 groups of leaning magnetic field lines of the leaning magnetic field of X, Y, Z for being rest frame 3 direction of principal axis are produced as the coordinate system of MRI device Circle 31 and the leaning magnetic field power supply 33 for driving each gradient magnetic field coil 31.By according to from sequencer 4 described later Order drives each leaning magnetic field power supply 33, so as to apply leaning magnetic field Gx, Gy, Gz on X, Y, Z this 3 direction of principal axis.Thus, The NMR signal (echo-signal) that can be produced to the irradiation in response to high-frequency impulse from detected body 1 assigns positional information.Specifically For, by the combination of this 3 groups of gradient magnetic field coils, the shooting section (sliced surfaces) of any direction can be set, and for The orthogonal and orthogonal both direction of the sliced surfaces carries out phase code or frequency coding to echo-signal.
Sending part 5 causes nuclear magnetic resonance for the nuclear spin of the atom of the bio-tissue to constituting detected body 1, And high-frequency impulse is irradiated to detected body 1, it possesses：High-frequency generator 51, modulator 53, high-frequency amplifier 55 and high-frequency line Enclose (hereinafter referred to as transmit coil) 57.The atom nuclear species for turning into shooting object in general MRI device is as detected body Main composition material hydrogen nuclei (proton).
In the timing provided by the instruction from sequence 4,53 pairs of RF arteries and veins from the output of high-frequency generator 51 of modulator are utilized Row amplitude modulation is rushed in, transmission line is supplied to after this is exaggerated by the high-frequency impulse after Modulation and Amplitude Modulation by high-frequency amplifier 55 Circle 57, the high-frequency impulse (hereinafter referred to as RF pulses) thus with defined amplitude and phase is irradiated to detected body 1.RF The amplitude of pulse, phase potential energy are adjusted using modulator 53 and high-frequency amplifier 55.
Transmit coil 57 is vertical magnetic field mode or horizontal magnetic field mode according to magnetostatic field generating unit 2, or according to being It is overall to be used with still local, and use the high frequency coil of various species.Transmit coil 57 is not limited in the present embodiment yet Species, but use the transmit coil of multiple passages with multipair supply terminals.In addition, in this manual, " the transmission of multichannel Coil " includes multiple coil, birdcage coils or the TEM (Transverse for being combined with multiple small coils Electromagnetic) coil it is such with multiple supply terminals to transmit coil.
As shown in Fig. 2 each passage of the transmit coil 57 of multichannel is connected with sending part 5 respectively, and by each passage quilt Driving.In addition, in fig. 2, exemplified with the transmit coil of 4 passages, but as long as port number would not be specially limited for more than 3. The magnetic field (hereinafter referred to as irradiating magnetic field) produced by the high-frequency impulse irradiated from the transmit coil 57 of this multichannel is Jiang Getong The magnetic field obtained after the irradiation magnetic field synthesis in road, is determined to irradiate Distribution of Magnetic Field by its combination.
In general, it is preferred to which it is spatially uniform to irradiate magnetic field, the amplitude for the RF pulses irradiated from each passage is adjusted And phase, to cause irradiation Distribution of Magnetic Field spatially uniform.The situation that amplitude and phase to the RF pulses are adjusted Referred to as RF shimmings, will determine that the amplitude and phase of each RF pulses of irradiation Distribution of Magnetic Field are referred to as RF shimming parameters.Irradiate magnetic field point Cloth also by the inherent magnetized influence of detected body, therefore RF shimmings need to each detected body (detected body it is every Individual shooting position) carry out.The details of the RF shimmings carried out in the MRI device of present embodiment is described below.
Acceptance division 6 detect because constitute detected body 1 bio-tissue atom nuclear spin nuclear magnetic resonance and The echo-signal of releasing, it possesses the high frequency coil (hereinafter referred to as receiving coil) 61, signal amplifier 63, orthorhombic phase of receiving side Position wave detector 65 and A/D converters 67.The echo-signal detected by receiving coil 61 after being amplified by signal amplifier 63, Split the letter for the two system being orthogonal by quadrature phase detector device 65 in the timing provided by the instruction from sequencer 4 Number, each free A/D converters 67 of signal of the orthogonal two system are transformed into digital quantity, and are sent to signal processing part 7.
The image pickup part of the MRI device of present embodiment by magnetostatic field generating unit 2 described above, leaning magnetic field generating unit 3, Sequencer 4, sending part 5 and acceptance division 6 are constituted.
Signal processing part 7 carries out various data processings and the display of result and preservation etc., and it possesses as computing The CPU81 in portion 8, additionally it is possible to possess the external memories such as CD or disk 71, display image and GUI etc. display part (display Device) 73 and input unit 75 etc..The various control information of the input MRI device of input unit 75, the processing carried out by signal processing part 7 Control information, it includes the input units such as tracking ball, keyboard, mouse, and constitutes user together with showing GUI display 73 Interface.That is, operator while the display picture of observation and input unit 75 close to the display 73 of configuration via input unit 75 Alternatively control the various processing of MRI device.
If data (echo-signal) are input to CPU81 from acceptance division 6, CPU81 performs signal transacting, Image Reconstruction etc. Processing, makes to be shown in display 73 as the image of the detected body 1 of its result, and be recorded in external memory 71. The image of detected body 1 is for example carried out including the spatial distribution to proton density, the spatial distribution for the relaxation time for encouraging state The morphological image of image conversion, function image.
Operational part 8 is sent out to sending part 5 and acceptance division 6 via sequencer 4 and instructed, and be controlled such that by Imaged according to defined pulse train.Pulse train provides the application intensity, fixed of high-frequency impulse and leaning magnetic field pulse When and echo-signal collect timing etc., various sequences are had according to the difference of image capture method, and in being stored in as program Portion's storage device or external memory.Operational part 8 is by reading and performing desired pulse train, so as to control to follow this The shooting of pulse train.
Operational part 8 is in addition to the control of above-mentioned shooting, also with calculating to the high frequency arteries and veins included in pulse train The function for the shimming parameter that the irradiation magnetic field of punching is determined.As already mentioned, the transmit coil 57 of present embodiment It is multichannel transmit coil, operational part 8 calculates shimming parameter by each passage of transmit coil, irradiation magnetic field is carried out optimal Change.In addition, optimizing not only comprising the such homogenization of existing MRI device.
The shimming parameter calculating section of present embodiment refers to realizing the work(that above-mentioned shimming parameter is calculated in the operational part 8 The part of energy.Operational part 8 is main to be made up of CPU81 and software, memory for being appended hereto it etc., but includes shimming parameter calculating section The some or all of the function of operational part inside can also pass through such as ASIC (Application of the hardware beyond CPU81 Specific Integrated Circuit), FPGA (Field Programmable Gate Array) etc. realize, and bag Containing in the present invention.
The MRI device of present embodiment is characterised by, when performing the pulse train comprising preparation RF pulses, makes preparation The shimming parameter of RF pulses and the shimming ginseng with preparing RF pulses separately apply excitation RF pulses for encouraging shooting position Number is different, so as to the description resolution ratio of the desired part of improving the shooting position.For example, being to make rule in advance in preparation RF pulses In the case of suppression RF pulses of the magnetic saturation in fixed region to suppress the signal from the defined region, enter to exercise the suppression Effect processed shimming partly different in defined region.On the other hand, for excitation RF pulses, enter to be about to irradiation magnetic field point The shimming that cloth is homogenized as region entirety.
Hereinafter, according to specific image capture method, the embodiment of the method for shimming of the MRI device of present embodiment is illustrated.
<First embodiment>
On the MRI device of present embodiment, application of the image pickup part after the preparation RF pulses for entering row energization to first area Afterwards, the application and NMR signal for performing comprising excitation RF pulses and encoding leaning magnetic field collect including pulse train, to the Two regions are imaged.As one, preparation RF pulses are the suppression RF pulses suppressed to the signal from first area, Pulse train is to be based on TOF method (time-of-flight methods：Time-of-flight method) pulse train.
In addition, the MRI device on present embodiment, shimming parameter calculating section passes through the shimming as preparation RF pulses Computing is repeated in parameter (the first shimming parameter), so that the irradiation Distribution of Magnetic Field calculated in desired position takes minimum value Shimming parameter.In addition, calculating the shimming parameter for the irradiation Distribution of Magnetic Field homogenization for making second area overall, excitation RF pulses are used as Shimming parameter (the second shimming parameter).
Hereinafter, in case of carrying out the shooting of the blood vessel using neck arteries as object, present embodiment is mainly illustrated MRI device operational part function and action.
The functional block diagram as shown in Figure 3 of operational part 8 of present embodiment possesses like that：ROI configuration parts 81, irradiation magnetic field Calculating section 82, shimming parameter calculating section 83, imaging control part 84, Image Reconstruction portion 85, display control unit 87, memory 89.This Outside, operational part 8 can also possess for calculating or setting beyond shimming parameter in addition to each several part shown in Fig. 3 Function for the condition of shooting.
ROI configuration parts 81 accept the information (coordinate) of 1 or multiple ROI inputted via input unit 75.Irradiate magnetic field Calculating section (B1 calculating sections) 82 calculates the irradiation Distribution of Magnetic Field in the defined shooting section of detected body 1 based on NMR signal. In example illustrated, B1 calculating sections 82 are shown but it is also possible to be independent as the One function of shimming parameter calculating section 83. Shimming parameter calculating section 83 is believed based on the irradiation Distribution of Magnetic Field calculated by B1 calculating sections 82 and by the ROI that ROI configuration parts 81 are set Breath, calculates the shimming parameter for generating defined irradiation Distribution of Magnetic Field.Here, transmit coil 57 be as shown in Figure 24 lead to Road transmit coil, and it is set to calculate the shimming parameter of each passage.
Imaging control part 84 set in sequencer 4 calculated by shimming parameter calculating section 83 shimming parameter, via The pulse train that input unit 75 is selected, and control image pickup part via sequencer 4.
Image Reconstruction portion 85 reconstructs the image of detected body using the data received by shooting by acceptance division 6. In the image of detected body in addition to the image at shooting object position, positioning image of acquirement etc. before shooting is additionally included in.
Display control unit 87 makes the image being made by Image Reconstruction portion 85 be shown in display 73 as display image, and The GUI that progress is shown in display 73 etc. control.
Before the action of explanation operational part 8, used in the blood vessel shooting for illustrating the MRI device based on present embodiment Pulse train.Fig. 4 shows that 3D-TOF sequences are used as one of the pulse train of blood vessel shooting.In Fig. 4, RF represents RF pulses Apply timing, Gs, Gp and Gr represent slice selection gradient magnetic field pulse, the pulse of phase code leaning magnetic field, read and incline respectively Regularly, Sig represents the generation of echo-signal for the application of oblique magnetic field pulse (pulse of frequency coding leaning magnetic field).
The pulse train is included：Apply the part 1 410 of suppression RF pulses 411 and from being applied excitation RF pulses 421 Part 2 420 untill echo-signal is measured, in part 1 410, simultaneously applies section with suppression RF pulses 411 and inclines Oblique magnetic field pulse 412, as shown in figure 5, row energization is entered in the detected body region (first area) 510 flowed through to arteria carotis, in advance First make the blood flow spin saturation flowed in arteria carotis stream.But, it is not to utilize to suppress the general of RF pulses 411 herein as described later First area 510 is equably encouraged, but according to inhibition in the preassigned ROI for making to be included in first area 510 The mode of decrease is encouraged.
In the part 2 420 of pulse train, with excitation RF pulses 421 simultaneously, apply the inclination with part 1 410 Magnetic field pulse 412 different section leaning magnetic field pulses 422 that sliced surfaces are carried out with selection encourage detected body head 520 (second area), is imaged to the arteria carotis stream flowed on head.Suppress the interval of RF pulses 411 and excitation RF pulses 421 It is configured to consider the position relationship and the reasonable time of VPV at the shooting position on neck and head.
After the application of excitation RF pulses 421 and section leaning magnetic field pulse 422, in slice direction and phase code Apply respectively on direction leaning magnetic field pulse 423,424 and apply reading leaning magnetic field 425 and obtain echo-signal 426 this Point and the leaning magnetic field pulse this point and the pulse train of common TOF methods in the after-applied phase reunion of signal acquirement It is identical.The pulse train of diagram is 3D pulse trains, therefore is tilted making section encode leaning magnetic field pulse 423, phase code While magnetic field pulse 424 and their phase reunion are changed with the intensity of leaning magnetic field pulse, echo is repeated The measurement of signal, obtains the three-dimensional data on detected body head 520.
In the pulse train of TOF methods, by with shorter interval repeatedly continuously measurement signal, so as to utilize blood flow Effect is flowed into describe blood flow spin.Therefore, in the case that in part 1 410, i.e. suppression RF pulses 411 do not apply, describe The blood flow for flowing to head from the neck arteries of left and right is overall.In present embodiment, by making based on the irradiation for suppressing RF pulses 411 Distribution of Magnetic Field is different with the irradiation Distribution of Magnetic Field based on excitation RF pulses 421, specifically, within for left and right arteria carotis One to adjust shimming parameter with to suppress irradiation magnetic field when RF pulses 411 are irradiated than another irradiation magnetic field it is small, There is no repressed state so as to cause an only arteria carotis.Thus, in the shooting of ensuing TOF methods, can only it retouch Paint an arteria carotis.
Next, centered on the calculating of the shimming parameter in shimming parameter calculating section 83, illustrating the action of operational part 8. Fig. 6 shows the flow of action.
First, before formal shooting, imaging control part 84 performs the space of each passage for obtaining transmit coil The shooting (S601) of the prescan and positioning image of sensitivity profile.Based on each spatial sensitivity profile obtained by prescan, Set the parameter (phase and amplitude) of each passage of transmit coil.In this case parameter can also be set with default value.
In addition, spatial sensitivity profile is stored in memory 89.It is, for example, with relatively low spatial discrimination to position image The image that rate is obtained after being imaged to the wider visual field, examiner can set section that should be imaged based on the positioning image Face, or specified Region Of Interest (ROI).
Operational part 8 (display control unit 87) makes to be shown in display part based on positioning image come the section for the first area specified 73, and accept specified (S602) of the ROI via input unit 75.Fig. 7 shows the picture example that ROI is specified.In the example in the figures, The section of presaturation region (first area) is shown as 700, examiner retouches in the images by using circular mark to specify The arteria carotis of the left and right drawn two, so that the positional information of arteria carotis is delivered into operational part 8, and is set in as ROI ROI In configuration part 81.Here, the ROI set in the arteria carotis for inhibiting signal is defined as into " ROI_T ", suppressed no Arteria carotis is that the arteria carotis for wanting to describe is defined as " ROI_F ".
In addition, as the image of ROI settings, the sectional view being made according to positioning image can also be replaced, and show root The irradiation Distribution of Magnetic Field B1 tried to achieve according to parameter (phase and amplitude) initial value of each passage of transmit coil.
Next, space of the shimming parameter calculating section 83 using each passage for the transmit coil 57 being stored in memory 89 (subscript n is 1~N integer to sensitivity profile B1n, and N represents port number.It is same as below) and set in ROI configuration parts 81 ROI information, calculates the shimming parameter (S603) for giving desired irradiation Distribution of Magnetic Field.
Therefore, first, irradiation magnetic field calculating section 82 using each passage spatial sensitivity profile B1n and each passage Phase n and amplitude A n, calculates irradiation Distribution of Magnetic Field (B1 figures) B1 of presaturation region entirety.Typically, irradiation Distribution of Magnetic Field B1 Represented by formula (1).
【Mathematical expression 1】
B1=∑s An exp(iφn)B1n (1)
Here, the irradiation Distribution of Magnetic Field B1 for using the initial value of shimming parameter (An, φ n) to be calculated using formula (1) is set to The initial value B1 of following calculating0。
Next, shimming parameter calculating section 83 is when the phase n and amplitude A n for making each passage there occurs change, by ROI_ The average value of B1 in F calculates the phase for minimizing the evaluation function and the group of amplitude as evaluation function f (following formula (2)) Conjunction is shimming parameter.
【Mathematical expression 2】
F=mean (B1 (ROI_F)) (2)
Evaluation function f is set to turn into calculating for minimum shimming parameter optimal known to such as can use steepest descent method Change algorithm.As the initial value of the B1 (ROI_F) in computing repeatedly, can use among the initial value B10 of irradiation Distribution of Magnetic Field, Distribution in ROI_F.In addition, as the constraints of computing repeatedly, setting does not change as the average value of the B1 in ROI_T Condition.That is, the average value of the B1 in B1 (ROI_T) is maintained initial value B1 as shown in formula (3)0ROI_T in be averaged Value B1 (ROI_T)0。
【Mathematical expression 3】
Mean (B1 (ROI_T))=B1o (ROI_T) (3)
In addition to above-mentioned constraints, specific absorption rate (SAR) SAR limitation can also be added as constraints. If it is considered that SAR and set the shimming parameter (An, φ n) set by initial value, then will be identical with SAR now or no more than this When SAR be set to constraints.If it is determined that the parameter of pulse train and the decision pulse train can then calculate SAR, it is calculated It is known to go out method, therefore in this description will be omitted.
Operational part 8 can also make the irradiation Distribution of Magnetic Field image according to obtained from the shimming parameter calculated be shown in display Portion 73 (S604).By the way that the irradiation Distribution of Magnetic Field image is for example shown side by side with the image that is used in ROI setting screens, Suitably carried out signal suppression so as to be confirmed whether to become ROI_T and ROI_F or do not suppressed by signal Irradiate Distribution of Magnetic Field.Wherein, result is shown in into this point of display part 73 to be not essential in the present embodiment.
Fig. 8 shows that the first area in the case of making shimming Parameters variation by present embodiment (is based on suppressing RF pulses Excitation area) irradiation Distribution of Magnetic Field change.Fig. 8 (a-1) is shown in initial B1 figure images to be set on its picture ROI_T and ROI_F.Fig. 8 (b-1) is used in the B1 in the irradiation magnetic field that the shimming parameter calculated in above-mentioned steps S603 is calculated Figure image.In two figures (a-1) (b-1) downside, show by (white line) place on ROI_T and ROI_F and the line parallel with X-axis Pixel value (corresponding with magnetic field intensity) (Fig. 8 (a-2) (b-2)).
Compared according to these it is recognized that while Distribution of Magnetic Field is homogenized and almost do not had in ROI_T and ROI_F when initial ROI_T magnetic field intensities compared with ROI_F are larger after difference, but shimming.That is, RF pulses are being irradiated with the irradiation Distribution of Magnetic Field In the case of, although the blood flow spin in ROI_T is energized, and the signal in ensuing TOF pulse trains is suppressed, but ROI_F Interior blood flow spin does not suppress signal, but is imaged according to effect is flowed into high-contrast.
Shimming parameter calculating section 83 using the shimming parameter calculated as the pulse train 400 shown in Fig. 4 suppression RF arteries and veins The shimming parameter (the first shimming parameter) of punching 411 is set in image pickup part (sequencer 4).
Next, shimming parameter calculating section 83 calculates the shimming parameter (at the shooting object position (second area) of TOF methods Two shimming parameters) (S605).The shimming parameter on head, which is determined into, makes the irradiation uniformity of magnetic field on head to be best.The uniformity Calculate for example using the evaluation function Usd represented by formula (4), calculate the shimming parameter for minimizing the evaluation function.
【Mathematical expression 4】
In formula, m (B1) and σ (B1) are B1 average value, standard deviation respectively.That is, Usd is standard deviation divided by B1 The value obtained after average value, B1 smaller then value of fluctuation is smaller, and the B1 uniformitys are higher.In addition, in Fig. 6 flow, One shimming parameter, which is calculated, carries out step S605 after step S603, but it is also possible to prescan before by shooting and obtained each After spatial sensitivity profile B1n, step S605 is directly carried out.
The shimming parameter calculated by step S605 as the excitation RF pulses 421 of Fig. 4 pulse train 400 shimming parameter (the second shimming parameter) is set in image pickup part (sequencer 4).
After the shimming parameter of each RF pulses 411,421 is so set, imaging control part 84 starts to image (S606). That is, imaged according to the pulse train 400 shown in Fig. 4, obtained the view data on the head as shooting position.Now, press down RF pulses 411 processed are irradiated with the first shimming parameter, and excitation RF pulses 421 are irradiated with the second shimming parameter.By swashing In the shooting section for encouraging the excitation of RF pulses 421, due to the blood flow spin in ROI_T because suppressing RF pulses 411 in the shape of saturation Flow into, therefore be suppressed from signal here under state.On the other hand, the blood flow in ROI_F is spun on certainly is not suppressed RF arteries and veins Punching 411 is flowed into shooting section in the case of suppressing, high RST is turned into according to effect is flowed into.That is, can only it be depicted It is selected as the image of ROI_F arteria carotis.
Fig. 9 shows to apply the image example of present embodiment.Fig. 9 (a) represents to eliminate the 1st of Fig. 4 pulse train 400 Part 410, i.e., the image obtained from the shooting without carrying out TOF methods in the case of pre-saturated.Fig. 9 (b), (c) difference table Show and ROI_F is set as left neck artery, right carotid, carry out the shooting of the pulse train comprising Fig. 4 including presaturation and obtain The image arrived.
In addition, in the case where obtaining 3D data using 3D pulse trains, Image Reconstruction portion 85 is not only made layer image, The 3D rendering for employing method known to volume drawing, MIP processing etc. can also be made.Display control unit 87 as needed will be by scheming As the image that reconstructing part 85 is made is shown in display part 73 (S607) together with detected body, the incidental information of shooting correlation.
More than, as described, according to present embodiment, using the suppression RF pulses of excitation first area and swashing Encourage the excitation RF pulses of the second areas different from first area to carry out during blood flow shooting, by the shimming for making suppression RF pulses Parameter with excitation RF pulses shimming parameter it is different so that optionally only by the blood flow flowed in first and second area it In desired blood flow carry out image conversion.Now, the high frequency of the RF pulse application time length as being encouraged without using so-called 2D Pulse, therefore, it is possible to suppress the long-time of time of measuring, SAR can also be suppressed to appropriate scope in addition.
More than, so that arteria carotis is illustrated into first embodiment in case of carrying out blood flow shooting as object, but Shooting object is not limited to arteria carotis, can regard various blood flows as object.In addition, in the above-described embodiment exemplified with 3D- The pulse train of TOF methods, but it is also possible to be 2D-TOF methods, also can be using known for coding direction, leaning magnetic field applying method Various modifications example.Further, sequence is imaged as the blood flow after presaturation, TOF methods can also be replaced and PC is used (Phase Contrast) method isopulse sequence.
In addition, in the above-described embodiment, being said to the input by accepting examiner to set ROI situation It is bright, but it is also possible to use the information such as pixel value, the area of determined pixel value of cross-sectional image by ROI configuration parts 81 according to position certainly Big arterial portions are detected dynamicly to set ROI.In this case, Fig. 6 ROI setting procedure S602 turns into based on ROI settings The ROI in portion 81 automatic setting procedure.
<The variation of first embodiment>
In the first embodiment, set two ROI (ROI_T, ROI_F), with suppress the signal from a ROI without The mode for suppressing the signal from another ROI sets shimming parameter, but the ROI set is not limited to two.Hereinafter, make For the variation of first embodiment, illustrate the situation for setting three ROI.The structure of device, the pulse train used etc. with First embodiment is identical, thus omit with first embodiment identical key element, the explanation of step, with first embodiment Illustrated centered on different points.In addition, as needed, quoting each figure of reference in the first embodiment.
Figure 10 shows to show the ROI setting screens example in the section of first area.As illustrated, flowed in head In artery except in first embodiment it is stated that in addition to 2 arteria carotis crossed, also vertebral arteries.In the present embodiment, Suppress the signal of any two arteries in 2 arteria carotis and vertebral arteries, only describe an artery.Therefore, ROI configuration parts 81 two ROI_T1, ROI_ that setting is suppressed to signal in blood flow describes (part 2 420 of Fig. 4 pulse train) A T2 and ROI_F of suppression without signal.
For example, being set to following setting：The signal of an arteria carotis in the arteria carotis of left and right and vertebral arteries is carried out Suppress, the signal of another arteria carotis in arteria carotis is not suppressed.It is same with first embodiment on ROI setting Sample, the disconnected of the region (first area) that RF pulses are suppressed by signal can be suppressed by the utilization of display as shown in Figure 10 Layer picture, and specifying for the ROI that examiner is carried out is accepted, so as to carry out ROI setting.In addition it is also possible to be automatically set.
Next, shimming parameter calculating section 83 using the above-mentioned 3 ROI positional information set by ROI configuration parts 81 with And the transmission sensitivity profile B1n of each passage of transmit coil obtained by prescan, being calculated by computing repeatedly makes by above-mentioned The shimming parameter that the evaluation function that formula (2) is represented is minimized.
Wherein, in this repeatedly computing, it is shown below like that, in two ROI_T1, ROI_T2, by first area The average value of irradiation Distribution of Magnetic Field, which does not change, is set to constraints.In this case, the constraintss such as SAR can also be added.
【Mathematical expression 5】
Mean (B1 (ROI_T1))=B1o (ROI_T1) (5-1)
Mean (B1 (ROI_T2))=B1o (ROI_T2) (5-2)
The shimming parameter so calculated is set in image pickup part, performs the pulse train shown in Fig. 4 to carry out the secondth area The shooting in domain is identical with first embodiment.
According to this variation, in the artery shooting on head, because the signal from vertebral arteries is also suppressed in the lump, because This can improve description resolution ratio when being imaged respectively to left and right arteria carotis.In addition, setting vertebral arteries as not In the case of the position (ROI_F) for suppressing signal, only vertebral arteries can be imaged.In addition, this variation is also not necessarily limited to The shooting of arteria carotis, other positions of belly flowed through for multiple big arteries can be applied to enter one of artery The situation of row shooting.
<Second embodiment>
Present embodiment is characterised by, calculates the shimming parameter of multiple suppression RF pulses, and progress repeatedly joins shimming The different shootings of number, the image at the position as target is obtained by the calculating between the image that is obtained by these shootings.
That is, the MRI device of present embodiment, shimming parameter calculating section is calculated and first in addition to the first shimming parameter The 3rd different shimming parameter of shimming parameter is used with above-mentioned first as the shimming parameter for preparing RF pulses, image pickup part The preparation RF pulses and the first of above-mentioned excitation RF pulses that shimming parameter is adjusted are imaged, use and joined with above-mentioned 3rd shimming The preparation RF pulses and the second of above-mentioned excitation RF pulses that number is adjusted are imaged and without using above-mentioned prepared RF pulses Obtained using the 3rd shooting of above-mentioned excitation RF pulses, and using in the above-mentioned first shooting, the second shooting and the 3rd shooting NMR signal form the image of above-mentioned detected body.
In the present embodiment, the structure of operational part is identical with the structure of the first embodiment shown in Fig. 3, therefore suitably Fig. 3 is quoted, is illustrated centered on the function of the operational part and image pickup part different from first embodiment.
The image pickup part and the action process of operational part of the MRI device of present embodiment are represented in fig. 11.In fig. 11, Show and omit the description with same-sign for the step identical with Fig. 6.
Then the measurement (S601) before, in ROI setting procedure S602, in the same manner as first embodiment, to 3 ROI for example sets ROI to two arteria carotis and vertebral arteries.These ROI are set to ROI_A (left neck artery), ROI_B (right necks Artery), ROI_C (vertebral arteries).Next, shimming parameter calculating section 83 calculates two shimming parameters (first and the 3rd even Field parameters) it is used as the shimming parameter (S6031, S6032) for suppressing RF pulses.First shimming parameter, which is for example determined into, makes irradiation magnetic Field distribution turns into minimum in ROI_A.
In other two ROI_B, ROI_C, do not changed using to irradiate the average value of Distribution of Magnetic Field and be used as constraints. 3rd shimming parameter, which is for example determined into, makes irradiation Distribution of Magnetic Field turn into minimum in ROI_B.In other two ROI_A, ROI_C In, do not changed using to irradiate the average value of Distribution of Magnetic Field and be used as constraints.In addition, for the secondth area as shooting position Domain also sets shimming parameter (the second shimming parameter) (S605).This can be the initial value set in prescan, and be to be determined Determine into the shimming parameter for homogenizing the irradiation Distribution of Magnetic Field of second area.
In addition, omitted in fig. 11, but with the step S604 of first embodiment it is equally possible that using The Distribution of Magnetic Field (B1 figures) produced by the irradiation of RF pulses is calculated and shows in the case of these shimming parameters.
Next, image pickup part performs 3 shootings (S6061) successively.The order of these shootings is arbitrary.In the first shooting In, in the pulse train 400 shown in Fig. 4, irradiate the suppression RF pulses adjusted with the first shimming parameter.Therefore, exist Then in the pulse train of the action, the signal beyond ROI_A (left neck artery) is suppressed, and obtains depicting left neck with high brightness The image of artery.In second images, the suppression RF pulses adjusted with the 3rd shimming parameter are irradiated, ROI_B are obtained (right Arteria carotis) beyond the repressed image of signal.In the 3rd images, without presaturation.That is, without shown in Fig. 4 TOF method pulse trains are performed in the case of the suppression RF pulses applying portion 410 of pulse train 400.Thus, it is dynamic from which The signal of arteries and veins is all suppressed, and obtains the image depicted according to inflow effect with high brightness.
Figure 12 represents that the signal in the first~the 3rd shooting suppresses the relation between resulting image.
As illustrated, by this 3 shootings, the image of left neck artery, the image of right carotid, three arteries are obtained Image.Image Reconstruction portion 85 obtains desired image by the computing in above-mentioned 3 images obtained in imaging.For example, logical Cross the view data obtained from being imaged the 3rd and difference is carried out to the view data obtained in being imaged first and second, from And the image of vertebral arteries can be obtained., can be to be easily mastered furthermore it is possible to obtain depicting the image of any 2 arteries Form relation of each artery etc. is shown in display part.
In addition, in the case where wanting to respectively obtain the image of 3 arteries, it is described in such as variation of first embodiment As bright, when suppressing the irradiation of RF pulses, can calculate each artery does not have repressed irradiation Distribution of Magnetic Field yet, to enter The shooting of row 3, but according to present embodiment or only 2 shootings calculate irradiation Distribution of Magnetic Field, can reduce and irradiate magnetic field Distribution calculates processing.
<3rd embodiment>
Pulse train based on ASL (Perfusion Imaging of Arterial Spin Labeling) method is set to object by present embodiment.Preparation RF Pulse is the preparation RF pulses that the blood flow spin flowed in first area is marked, to the blood flow by preparation RF pulse labelings The flowed into second area of spin is imaged.
ASL methods are following methods：That is, perform to blood flow spin be marked and carry out signal measurement pulse train and The pulse train of signal measurement is carried out in the case where blood flow spin not being marked as control, to by two pulse trains Obtained image carries out difference, so as to describe perfusion.In mark processing, blood flow is located to the position relative to desired shooting The position irradiation preparation RF pulses of upstream portion, make the blood flow spin flip conversion at the position.In control process, handled with mark Identical position, applying does not make blood flow spin flip conversion, i.e. position magnetization turn into 0 degree of such preparation RF pulses (control RF pulses).
For example, in the case of being head 530 at shooting position as shown in Figure 13, to the blood flow of neck 540 from precession Line flag processing/control process.Handling from mark/control process respectively through the stipulated time after, selection target Position 530 is imaged, blood flow camera pulse sequence is performed, obtains view data.
It is used as the preparation RF pulses used in mark processing and control process, such as known following spike train：90 degree Pulse：180 degree pulse：Spike train as 90 degree of pulses is used as mark, 90 degree of pulses：180 degree pulse：- 90 degree pulses this The spike train of sample as control use, etc., in the present embodiment, be not also particularly limited, use known prepared RF arteries and veins Punching.
As blood flow camera pulse sequence, it can use and use stream encryption pulse (VENC) after excitation RF pulses apply The pulse train based on PC methods, echo-signal collection in using GrE-EPI (gtadient echo planar process), FSE (at a high speed spin Echo method) etc..Figure 14 shows one of the pulse train 800 of ASL methods.
Here, in order that explanation simply, only shows that RF pulses 801,802 and VENC803 application timing are received with signal 804 are taken, the leaning magnetic field for selection of cutting into slices is omitted, encodes leaning magnetic field.In addition, by the pulse train of mark and controlling arteries and veins Sequence is rushed to be set shown in.In the pulse train, as illustrated, it is located at upstream relative to the blood flow at shooting position in selection Position (such as neck 540) and be applied with mark with or the preparation RF pulses 801 of control after, separating the defined time applies Plus enter the excitation RF pulses 802 of row energization to shooting position 530.After excitation RF pulses 802 apply, apply VENC pulses 803, In the state of coding leaning magnetic field as defined in giving, echo-signal is obtained.
Here, preparation RF pulses 801 and the excitation respective shimming parameters of RF802 are independently set.First, for preparation RF pulses 801, set shimming parameter, to cause among flowing through the blood flow of first area 540, beyond the desired blood vessel described Vasculature part, irradiation Distribution of Magnetic Field diminishes.That is, for the region encouraged by preparation RF pulses 801, based on 2 set in advance ROI_T, ROI_F, calculate shimming parameter, make it that the average value of irradiation Distribution of Magnetic Field of one (ROI_T) does not change, and Turn into minimum in another (ROI_F).
The RF pulses of RF pulses and the control of mark are set to identical shimming parameter.For excitation RF pulses 802, calculate Go out integrally makes the uniformity in irradiation magnetic field optimize the shimming parameter of (uniformity highest) as shooting position.These shimming parameters Calculation method it is identical with the method illustrated in first embodiment.When calculating, set in the first region in shimming parameter Multiple ROI this point and calculated shimming parameter is set in image pickup part and pulse train this point is performed also with first Embodiment is identical.
In the case where setting shimming parameter as above, in the small blood vessel (ROI_F) of irradiation Distribution of Magnetic Field, due to The blood flow spin for flowing through there is flowed into image pickup part because mark keeps not being labeled in the state of (reversion) with preparation RF pulses The difference of obtained image and the image obtained after control process there's almost no behind position, therefore mark processing, thus obtain with Inhibition identical effect be not depicted in ASL, i.e. signal.On the other hand, due to maintaining larger irradiation magnetic field The blood flow at position (blood vessel) (ROI_T) be labeled from being spun in mark reason, turn into magnetization zero in control process, therefore logical Difference processing is crossed by image conversion.That is, can by reducing irradiation Distribution of Magnetic Field of the mark with preparation RF pulses at defined position Optionally describe the position of irradiation magnetic field big (maintaining the average value of irradiation Distribution of Magnetic Field).
In addition, for present embodiment, also the variation with first embodiment is it is equally possible that set more than 3 ROI, can also be as second embodiment, changing the shimming parameter of preparation RF pulses to obtain multiple makes the portion to be suppressed The different image in position, the image at desired position is obtained by the computing between image.
For example, in the 1st time images, so that mark/control is imaged with the irradiation Distribution of Magnetic Field and blood flow of preparation RF pulses Shimming parameter that any one uniformity of the irradiation Distribution of Magnetic Field of excitation RF pulses of sequence is optimized is performed, and is taken the photograph at the 2nd time As in, as irradiation Distribution of Magnetic Field of the mark/control with preparation RF pulses, with the shimming parameter suppressed to defined blood vessel To perform.Moreover, the image obtained in being imaged by the image obtained from the 1st shooting to the 2nd time carries out difference, so as to Access the image for optionally depicting defined blood vessel.
According to present embodiment, in based on the perfusion of ASL methods shooting, it can be retouched target tightening in desired blood flow Paint the state of perfusion.
More than, each embodiment to the MRI device of the present invention is illustrated, but the pulse illustrated in each embodiment Sequence, shooting position are one, are not limited to these situations, as long as include 2 RF for entering row energization to different regions respectively Camera method including pulse is with regard to that can apply.
Utilization possibility in industry
According to the present invention, there is provided a kind of side for describing desired position using the method choice different from selection excitation Method.

Claims (14)

1. a kind of MR imaging apparatus, it is characterised in that possess：
Image pickup part, with the multichannel transmit coil that high-frequency impulse is irradiated from each passage of multiple passages, using comprising to quilt The first area of detection body enters the preparation RF pulses of row energization and a pair second area different from above-mentioned first area enters row energization Excitation RF pulses including high-frequency impulse collect NMR signal；And
Shimming parameter calculating section, calculates and the irradiation Distribution of Magnetic Field that the high-frequency impulse by being irradiated from above-mentioned multiple passages is produced is entered The shimming parameter of row adjustment,
Above-mentioned shimming parameter calculating section is calculated and the second shimming as the shimming parameter for being configured to above-mentioned excitation RF pulses The first different shimming parameter of parameter, is used as the shimming parameter of above-mentioned prepared RF pulses,
Above-mentioned image pickup part is used the preparation RF pulses adjusted with above-mentioned first shimming parameter and joined with above-mentioned second shimming The number excitation RF pulses that are adjusted are imaged.
2. MR imaging apparatus according to claim 1, it is characterised in that
Above-mentioned shimming parameter calculating section calculates above-mentioned first shimming parameter, to cause by above-mentioned prepared RF pulses above-mentioned first The irradiation Distribution of Magnetic Field produced in region is that irradiation magnetic field is smaller than second position in first position.
3. MR imaging apparatus according to claim 2, it is characterised in that
Above-mentioned shimming parameter calculating section the average value for the irradiation Distribution of Magnetic Field not made in above-mentioned second position is changed as Constraints, carries out computing repeatedly, calculates above-mentioned first shimming parameter.
4. the MR imaging apparatus according to Claims 2 or 3, it is characterised in that
Specific absorption rate when above-mentioned shimming parameter calculating section will irradiate above-mentioned prepared RF pulses with above-mentioned first shimming parameter is not More than the irradiation Distribution of Magnetic Field for making to produce in above-mentioned first area the uniformity optimize in the case of specific absorption rate make For constraints, computing repeatedly is carried out, above-mentioned first shimming parameter is calculated.
5. MR imaging apparatus according to claim 2, it is characterised in that
The MR imaging apparatus is also equipped with input unit, and the input unit accepts specifying for the position in above-mentioned first area,
Above-mentioned shimming parameter calculating section is directed to the position specified via above-mentioned input unit, calculates above-mentioned first shimming parameter.
6. MR imaging apparatus according to claim 5, it is characterised in that
Above-mentioned input unit includes display part, and the display part shows comprising the detected body image including above-mentioned first area and used In the GUI that above-mentioned position is specified on above-mentioned detected body image.
7. MR imaging apparatus according to claim 6, it is characterised in that
Above-mentioned detected body image be to as shooting object above-mentioned detected body image obtained from morphological image or Person irradiates Distribution of Magnetic Field image.
8. MR imaging apparatus according to claim 1, it is characterised in that
Above-mentioned shimming parameter calculating section calculates the shimming ginseng homogenized to the overall irradiation Distribution of Magnetic Field of above-mentioned second area Number, is used as the second shimming parameter.
9. MR imaging apparatus according to claim 1, it is characterised in that
Above-mentioned shimming parameter calculating section calculates the threeth shimming parameters different from above-mentioned first shimming parameter, is used as above-mentioned preparation The shimming parameter of RF pulses,
Above-mentioned image pickup part is used the preparation RF pulses adjusted with above-mentioned first shimming parameter and above-mentioned excitation RF arteries and veins First shooting of punching, use the preparation RF pulses that are adjusted with above-mentioned 3rd shimming parameter and above-mentioned excitation RF pulses the Two shootings and the 3rd shooting without using above-mentioned prepared RF pulses using above-mentioned excitation RF pulses, and using above-mentioned the Obtained NMR signal forms the image of above-mentioned detected body in one shooting, the second shooting and the 3rd shooting.
10. MR imaging apparatus according to claim 9, it is characterised in that
The above-mentioned first shimming parameter that above-mentioned shimming parameter calculating section is calculated is in above-mentioned firstth area by above-mentioned prepared RF pulses The shimming parameter that first position of the irradiation Distribution of Magnetic Field produced in domain in above-mentioned first area diminishes, above-mentioned 3rd shimming ginseng Number is the irradiation Distribution of Magnetic Field produced by above-mentioned prepared RF pulses in above-mentioned first area different from above-mentioned first position The shimming parameter that diminishes of second position.
11. MR imaging apparatus according to claim 1, it is characterised in that
The application of above-mentioned image pickup part then above-mentioned prepared RF pulses, is performed comprising above-mentioned excitation RF pulses and coding leaning magnetic field Application and NMR signal collect including pulse train, above-mentioned second area is imaged.
12. MR imaging apparatus according to claim 11, it is characterised in that
Above-mentioned preparation pulse is the suppression RF pulses suppressed to the signal from above-mentioned first area, and above-mentioned pulse train is Based on the pulse train of TOF methods, wherein, TOF methods are time-of-flight methods.
13. MR imaging apparatus according to claim 11, it is characterised in that
Above-mentioned preparation pulse is the preparation RF pulses that the flowing spins flowed in above-mentioned first area are marked, above-mentioned arteries and veins It is the pulse train based on ASL methods to rush sequence, wherein, ASL methods are Perfusion Imaging of Arterial Spin Labeling methods.
14. a kind of MR imaging method, using the high frequency coil of multiple passages, continuously irradiates the firstth area to detected body Domain prepare the first RF pulses of excitation and pair second area different from above-mentioned first area enters the 2nd RF arteries and veins of row energization Bring and above-mentioned second area imaged, the MR imaging method is characterised by,
Make the irradiation Distribution of Magnetic Field of above-mentioned 2nd RF pulses different from the irradiation Distribution of Magnetic Field of above-mentioned first RF pulses.
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